<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1, user-scalable=no">
    <title>Title</title>
    <style>

    </style>
</head>
<body>
<script>
    /*
    * debug
    *
    *
    *   chrome的source，然后看某个变量选中然后右击去watch
    *
    *
    *
    *
    *
    *
    *
    *
    *
    *
    * */
    alert(d)
    var b = 'hello world'
    var a = 123
    c = true;
    function fun(){
        a = 10;
    }
    var d = 45;
</script>
</body>
</html>